Yea in one of the further Ender's Game novels they talk about this tech a lot for characters silently mumbling to the AI.
That's exactly where my mind went. Something I've wanted ever since I read that book a couple decades ago.
There's some lesson there...
I really like Xenocide as well, but the series starts to decline from here on.
My first thoughts was Cory Doctorow's Down and Out in the Magic Kingdom. They call is "subvocal" or "subvocalizing" in the novel as well. Not saying he came up with the term though, just pointing it out.
You can read the whole thing for free on his website: https://craphound.com/down/Cory_Doctorow_-_Down_and_Out_in_t...